Saving a 50 Year-old Dam - Country's Longest-reaching Boom Pump Helps Preserve Dam March 1999

Pump worked from a platform in the middle of the Wenatchee River

When the old Tumwater Dam in Leavenworth, Wash., needed its spillway refaced, the contractor knew he would need the largest pump he could find to tackle the job. So Mowat Construction and Ralph's Concrete Pumping responded with the longest-reaching boom pump in the country – the Putzmeister 55-Meter.

Built in the early 1900s, Tumwater Dam once produced hydroelectric power for the area. But for the last 40 years, it has been abandoned. As a result, the rushing Wenatchee River and time took its toll on the 310-foot structure. In addition, the area's annual heavy spring snowmelt placed additional stress on the dam, creating the danger of a wash out in the area.

Not only would the repairs be difficult, but positioning the equipment would also be equally challenging. First, the water needed to be diverted to allow access to the site.

Then, to reach the dam and comply with environmental concerns, a 70-foot platform, projecting over the riverbed from the shore, was built for the 100,000-pound truck. After the truck was maneuvered down the steep incline, it was driven onto the platform where it deployed its outriggers on heavy-strength steel plates positioned on rocks at one side and on the riverbed at the other side.

In addition, the steep embankment prevented access to ready-mix trucks. So a 28-Meter truck was positioned on the road above the river and placed concrete into the hopper of the 55-Meter below. From the middle of the river and over a three-day period, the 55-Meter boom pump reached the L-shaped dam and placed more than 1,000 yards of concrete.

"The 180-foot boom of the 55-Meter was the only way to reach the area," said Harvey Pegg, project superintendent of Mowat Construction, the general contractor for the job. "It certainly worked to our advantage that Ralph's had the 55-Meter pump in the state of Washington."

Work on the $700,000 project started just after Labor Day and was completed six weeks later.